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Executive Summary

The expression “Nine Dragons Rule the Waters” has long been used to describe the contentious and fragmented roles and responsibilities of government agencies managing water in China. In the 1980s economic reform era, these competing and overlapping “dragons” often produced poor and contradictory policies that failed to reign in water pollution from China’s rapid urbanization and industrialization. In 2001, when Beijing was chosen to host the 2008 Summer Olympics, untreated wastewater and agricultural runoff had turned many of China’s rivers black and numerous large lakes were green with toxic algae blooms. At that time, despite wastewater treatment regulations, nearly 80 percent of China’s sludge went untreated, making it a growing source of methane emissions—a potent greenhouse gas. 1

China’s mountains of municipal and industrial sludge and lack of rural wastewater treatment sparked Xi Jinping to declare wastewater a major part of his “war on pollution” in 2018. However, treating wastewater and sludge can be an expensive battle to wage. To advance its wastewater and carbon reduction targets, China can learn from cities such as New York, Washington DC, and Singapore to tap three marketable resources from sludge to close the loop on wastewater. Specifically, Chinese wastewater plants can: (1) capture methane to generate low-carbon power, (2) treat sludge digestate to make compost, and (3) recycle the wastewater to meet multiple municipal and industrial water needs. All three bring down the costs of wastewater and sludge treatment as methane can power wastewater treatment plants and the digestate and recycled water can be sold.

Views expressed within this report are the author’s own and not necessarily those of the U.S. Government.

Methane: Turning Wastewater Gas into Power. Methane, a greenhouse gas produced when sludge decomposes, has an environmental impact 84 times greater than carbon dioxide. 2 The wastewater sector accounts for 10 percent of global methane emissions; 3 China is responsible for one-quarter of these emissions. Wastewater treatment plants (WWTPs) can capture methane through anaerobic digestion (AD)—a process in which microorganisms break down organic material in the wastewater in a digester tank. 4 The captured methane gas can be converted into electricity or vehicle fuel. 5

Digestate: Utilizing Brown “Gold.” Digestate (a.k.a. biosolids) produced in the AD process can be further dried and treated to be sold as organic compost, preventing the potentially toxic solids from being dumped into landfills and waterways. This compost can be used on urban rainwater gardens and green spaces to help reduce stormwater flood risks in China’s megacities.

Recycled Wastewater: Quenching Thirsty Cities. Recycled wastewater provides an alternative tap for the water-scarce nation. Recycled wastewater can recharge aquifers, irrigate landscapes and agriculture, and supply water to local industries. China’s available per capita water supply is one-fourth the world’s average 6 and China only reclaims approximately 4 percent of its wastewater. 7

Productively using methane, digestate and recycled water could help China’s wastewater plants become more financially resilient, but they face challenges implementing measures to increase their climate resiliency. Like many cities in the United States, during extreme rain and hurricane events many of China’s combined sewer systems and wastewater treatment infrastructure release sewage, flooding streets and contaminating drinking water sources. To increase the resiliency of wastewater systems, Chinese cities can follow New York City’s lead by implementing green infrastructure, such as permeable pavement and catchment areas, and controlling public water usage to reduce the volume of stormwater entering drains.

A CLOSED-LOOP FUTURE

While Chinese cities can profit from methane capture, digestate use, water recycling, and measures to increase climate resiliency, economic challenges make implementation difficult. China’s treatment plants often operate at a loss and managers are hesitant to invest in long return-on-investment projects. Additionally, finding customers for wastewater byproducts is difficult in China’s state-driven economic model. Beijing policymakers could set higher water prices and increase subsidies to raise capital for water utilities looking to implement methane capture. Cities can also leverage existing policies to create demand for wastewater methane, digestate, and recycled water, enabling China’s wastewater sector to reduce greenhouse gas emissions, remediate soil, and increase water security.

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